Improved graphite writing and drawing lead



Patented Jan. 29, 1935 UNITED STATES PATENT. OFFICE IllIPROVED GRAPHITE WRITING AND DRAWING LEAD N Drawing. Application August 10, 1931, Serial No. 556,303. In Germany December 8, 1930 2 Claims.

My invention relates to the production of leads for writing and drawing pencils to be used for preparing documents and drawings which are intended to be directly reproduced by means of 5 prints, especially blue prints. The ordinary pencil leads, which are saturated with fatty material (tallow, stearine, wax and the like), for the purpose of improving their writing capability, are ill-suited for the purpose, since the fat addition,

which occupies a considerable portion of the volume weight of the lead, increases the light transparency of the marks produced withv the lead.

According to my invention the fatty material serving for the production of the graphite leads, is

mixed with a fat-soluble colouring material such as the Sudan dyes specifically disclosed in my corresponding British Patent 383,330 of 1932. For example, colouring materials may be used which are made similarly to those usual in the production of carbon paper.

The light opacity of the lead is substantially raised by the present invention. The writing or drawing leads made according to the invention give a mark which, by working on tracing paper and producing light prints directly, yields a very sharp copy. 5

Having now particularly described and ascertained the nature of my said invention and in what manner the same is to be performed, I declare that what I claim is:

1. A process for producing graphite writing 10 and drawing leads adapted for preparing documents and drawings intended to be directly reproduced by means of light prints, consisting in incorporating with a graphite lead composition a fatty material containing fat soluble coloring 15 matter.

2. A writing and drawing lead, consisting of graphite lead composition and a fatty material containing fat soluble coloring matter.

20 KARL KREUTZER. 

